Measurement overview

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1 Measurement overview The EU Physical Agents (Artificial Optical Radiation) Directive Meeting Globe Room, Bushy House 23 rd May 2007 Simon Hall NPL

2 Outline Artificial Optical Radiation Directive measurements Photobiological Hazard Current optical radiation safety standards Measurement requirements Recommended techniques Apparent source size

3 EU Physical Agents Directive EU Physical Agents (Artificial Optical Radiation) Directive The proposal lays down minimum health and safety requirements regarding the exposure of workers to the risks arising from optical radiation. Based on ICNIRP guidelines for exposure levels. The proposal places a range of duties on employers. These include the requirements to assess and control exposure, reduce risk, and provide information and training to workers. There are also provisions on health surveillance.

4 AORD implications: Workplace Measurement (1) It is not expected that workplace measurement will be the norm Situations with multiple optical sources which approach the exposure limits incorporated in the directive may require measurement This may be a simpler alternative to complex calulation of the posssible interactions of the installed sources with each other and the physical structure of the workplace.

5 AORD implications: Workplace Measurement (2) Methodologies for measurement of mutiple sources and a robust traceability route will be required for situations where questions may arise over the potential hazard of optical radiation in the workplace. From the directive: the employer, in the case of workers exposed to artificial sources of optical radiation, shall assess and, if necessary, measure and/or calculate the levels of exposure to optical radiation to which workers are likely to be exposed so that the measures needed to restrict exposure to the applicable limits can be identified and put into effect. The methodology applied in assessment, measurement and/or calculations shall follow the standards of the International Electrotechnical Commission (IEC) in respect of laser radiation and the recommendations of the International Commission on Illumination (CIE) and the European Committee for Standardisation (CEN) in respect of non-coherent radiation.

6 AORD implications: Workplace Measurement (2) In exposure situations which are not covered by these standards and recommendations, and until appropriate EU standards or recommendations become available, assessment, measurement and/or calculations shall be carried out using available national or international science-based guidelines. The rapidly evolving availability and subsequent use of intense light sources in industrial, domestic medical and research environments will require increasing measurement rigour by manufacturers and integrators to ensure that these products will not generate problems for UK employers wishing to use their products.

7 International Standards used for Optical Radiation Safety IEC :2007 Ed. 2.0 IEC 62471:2006 Ed. 1.0

8 Free Space Optical Communication system locations An example of how a system for controlling problematic exposure levels can work

9 Medical Exposure Theatre Lights Treatment Laser Scalpels, IPL etc. Diffuse Light Dignostics OCT, Laser Doppler etc.

10 Exposure Limits for Optical Radiation International Commission on Non-Ionising Radiation Protection (ICNIRP) Exposure Limits for optical radiation Laser Non-Laser IEC IEC 62471

11 Introduction to photobiological hazards Radiation absorbed by the skin and cornea UV: 200 nm to 400 nm IR: 780 nm to >3000 nm 200 nm to >3000 nm

12 Introduction to photobiological hazards Radiation is transmitted and focused by lens 300 nm to 1400 nm

13 Hazard Exposure Limits (EL) Actinic UV hazard exposure limit for skin and eye Spectral irradiance 200 nm 400 nm S uv (λ) actinic UV hazard weighting function

14 UV Hazard Function UV Hazard Function S UV(λ ) 1.E+00 1.E-01 1.E-02 1.E-03 1.E-04 1.E Wavelength / nm

15 Hazard Exposure Limit (EL) cont. Actinic UV hazard exposure limit for skin and eye Spectral irradiance 200 nm 400 nm S uv (λ) actinic UV hazard weighting function Near-UV hazard exposure limit for the eye Spectral irradiance 315 nm 400 nm total radiant exposure < 10,000 J m -2 Retinal blue light hazard exposure limit Spectral radiance nm Spectral irradiance for small sources B(λ) blue light hazard weighting function

16 Blue Light Hazard Weighting Function Blue Light Hazard Function B (λ ) / no units Wavelength / nm

17 Hazard Exposure Limit (EL) cont. Retinal thermal hazard Spectral radiance 380 nm 1400 nm Spectral radiance 780 nm 1400 nm for weak visual stimulus R(λ) burn hazard weighting function

18 Burn Hazard Function 10 Burn Hazard R (λ ) / no units Wavelength / nm

19 Hazard Exposure Limit (EL) cont. Retinal thermal hazard Spectral radiance 380 nm 1400 nm Spectral radiance 780 nm 1400 nm for weak visual stimulus R(λ) burn hazard weighting function Infrared radiation hazard exposure limits for the eye Spectral irradiance 780 nm 3000 nm maximum radiant exposure W m -2 Thermal hazard exposure limit of the skin Spectral irradiance 380 nm 3000 nm total radiant exposure 20,000 t 0.25 J m -2 (t 10 s)

20 Optical safety standards cont Different requirements between standards for Laser and Non-Laser Optical radiation

21 Requirement for Testing CE Marking Low Voltage Equipment (LVD) 73/23/EEC Machinery Directive 89/392/EEC (Amended 98/37/EEC) Electrical Equipment (Safety) Regulations (LVD) Supply of Machinery (Safety) Regulations 1992 BS EN Safety of laser products BS EN Safety of machinery - Assessment and reduction of risks arising from radiation emitted by machinery

22 Measurement requirements 1 White Blue Green Amber Red Relative Spectral Power Distribution Wavelength (nm) + = Spectroradiometry

23 Irradiance / Exposure Units Hazard Name Relevant Equation Wavelength Range nm Exposure Duration sec Limiting Aperture rad (deg) EL in terms of constant irradiance W m -2 Actinic UV E S = skin & eye Eλ S( λ) Δλ < (80) 30/t 400 nm E λ 315 nm Eye UV-A E = Δλ Blue-light small source UVA EB = Eλ B( λ) Δλ nm E λ 780 nm 3000 nm E λ 380 nm Eye IR E = Δλ IR 1000 > > > (80) < (80) 10000/t 10 30/t /t Skin E H = thermal Δλ < 10 2π sr 20000/t 0.25

24 Radiance Units Hazard Name Relevant Equation Wavelength Range nm Bluelight L B = Lλ B( λ) Δλ Exposure Duration sec < Field of View radians (t/10) t (t/10) EL in terms of constant radiance -1-2 sr W m 10 6 /t 10 6 /t 10 6 /t 100 Retinal L R = thermal Lλ R( λ) Δλ /(α t 0.25 ) Retinal 1400 nm Thermal LIR = (weak L λ R( λ) Δλ > /α 780 nm visual stimulus)

25 Recommended Measurement Methods

26 Detector Array Spectrometer Integrating sphere Source Light guide Dispersion grating Polychromator Detector array Mirror 2 Mirror 1

27 Photometer 1.2 f1' ~ 13% for both photometers V(lambda) Phot 1 Phot

28 Radiance optics Angle of acceptance γ = α max = 100 mrad or γ = α min = 1.5 mrad

29 Radiance optics cont

0 Spectral Power Distribution 0.8 0.6 0.

30 Apparent Source Size Retinal Thermal Damage 1.0 Spectral Power Distribution Wavelength (nm) SPD and power of radiation Passing through iris Size of retinal image Duration of exposure

31 Apparent Source Size

32 Angular Subtense cont α max = 100 mrad α min = mrad

33 What is the apparent source of an LED? reflector reflected ray direct rays dome lens substrate chip

34 Extended Sources LED array

35 LED Beam Propagation

36 Angular subtense measurement

37 Experimental apparatus

38 Thank you for your attention Optical Technologies and Scientific Computing Team Acknowledgement to D Gibbs for assistance with this presentation

JAWIRA TIMUR SDN. BHD.,

JAWIRA TIMUR SDN. BHD., SIRIM QAS International Sdn.Bhd. (410334-X) No.1, Persiaran Dato Menteri, Section 2, P.O.BOX 7035, 40700 Shah Alam, Selangor Darul Ehsan, Malaysia. Tel: 03-55446252 Fax: 03-55446272 www.sirim-qas.com.my